Process for obtaining hydrocarbons from wells



Sept. 20, 1932. w. K. I Ewlsv 1,877,916

PROCESS FOR OBTAINING HYDROCARBONS FROM WELLS Filed July 28. 1928 CA T .EZCHANG'ER To GAS c LNE REC' OVER? SYS TEM To .5 roRA GE 2 O IN L. nl 1 ,l 1&1 R1 I vento/c W/I/Lwz/Yx/w Patented Sept. 20, 1932 UNITED STATES PATENT 'OFFICE WARREN K. LEWIS, OF NEWTON, MASSACHUSETTS, ASSIGNOR TO STANDARD OIL DEVELOPMENT COMPANY, A CORPORATION F DELAWARE PROCESS FOR OBTAINING HYDROCARBONS FROM WELLS Application led 'July 28, 1928. Serial No. 296,007.

The present invention relates to an improved process for obtaining petroleum products and more specifically comprises a method for obtaining gaseous and liquid hydrocarbons from the earth. My method will be understood from the following description and the drawing which illustrates the use of my process.

The drawing is a'semi-diagrammatic View in elevation of an apparatus for accomplishing my method and indicates the How of gas.

In the production of natural gas and natural gas gasoline from gas wells, it is customary to apply vacuum to the wells when the pressure has decreased to atmospheric pressure or thereabout and the natural fiow has declined. The gas obtained under subatmospheric pressure is compressed and cooled to obtain natural gas gasoline. It has been observed that the quantity of gas and gasoline decreases as time goes on although the gasoline content of the gas may increase. Vacuum of 20-27 inches of mercury below atmospheric pressure at the casing head is the highest to which it has been heretofore profitable to attain due to the decrease in production. I have discovered methods by which the yield of natural gas gasoline may be greatly increased and in conjunction with which vacuum exceeding 28 and 29 or even 29.5 inches of mercury below atmospheric pressure are desirable.

Referring to the drawing, reference character 1 designates the casing head of a natural gas well which may be constructed in the customary manner. Line 2 conducts natural gas which is under a reduced pressure to a refrigeration chamber 3 through which the gas is passed in Contact with a refrigeration coil 4, to be described below. Cooling is sufficient to produce a condensate which is collected in trap 5 and may be withdrawn to storage (not shown) by line 5a. It is preferred to pass the condensate and vapor through a heat exchanger 6.v Vapor then passes thru a second exchanger 6a to a vacuum pump 7 and compressed vapor is discharged through line 8, heat exchanger 6a, to a recovery system (not shown), which may be of any known` type for removing gasoline from the residual gas, such as oil absorption, adsorption by means of charcoal or other solids or compression.

Line 9 is fed with a material capable of producing a considerable refrigerating effect by expansion. Common refrigerants, such as ammonia and other easily liquetiable gases may be used, but I prefer to use propane or a mixture of hydrocarbons containing a substantial quantity of propane. The refrigerant is preferably under high pressure and may be cooled-by passage through exchanger 6. The refrigerant is then expanded through valve 10 into coil 4 in the refrigeration chamber. The expanded refrigerant is returned by line 11 to a compressor 12, cooler 13 and again to line 9.

In the operation of my process, heating of the natural gas before entering vacuum pump 7 greatly increases the yield of gasoline obtainable from the well. It has been observed that as time goes on the gas becomes richer in gasoline and 'I find that the dew point of the gaseous mixture, measured at atmospheric pressure, gradually rises. Furthermore, I have found that unlike steam and many other vapors, compression of vapors of normally liquid hydrocarbons or mixtures of the same, even under adiabatic conditions, does not tend to produce a superheated Vapor, but on the contrary tends to cause condensation of hydrocarbon liquid. It will be understood that cooling during compression greatly increases ,the tendency toward condensation. It is desirable to prevent such condensation in the vacuum pump cylinders since all of the liquid can not be removed from the cylinder on the exhaust stroke and reevaporation tends to reduce the pump capacity and cut down the attainable vacuum. It is therefore desirable to increase the range of temperature through which compression may occur without simultaneous condensation. This may be accomplished byraising the temperature of the gas before or during compression but I prefer just to reduce the dew point of the gas by removal of a portion of the higher boiling hydrocarbons which are most readily condensed then preferably to reheat residual vapor before compression.

In the system illustrated, -the refrigeration chamber 3 may be eliminated and the temperature of the gas raised by heating, say with steam` in exchanger 6. I contemplate opera- 5 tion in this manner but I prefer to remove a portion ofthe higher boiling constitutents of the gas and thereby reduce its dew point.

While I prefer ',to reduce the dew point by refrigeration 'and subsequently to heat lthe gas before passage -into the vacuum pump,

the same result may be accomplished by absorption of the higher boiling constituent in oil before compression or by absorbing such constituents on charcoal.

By the term reducing the dew point I mean treating the vapor mixture in such a manner that it may be cooled to a lower temperature without encountering incipient condensation.`

My process is particularly adapted to use in oil and gas wells, in which the absolute pressure is below about 1 or 1/2 of mercury where the volumetric efficiency of the pump begins to decrease seriously. Indeed, the effect of the reevaporation of condensate becomes much greater as the absolute pressure is reduced. Altho my process is particularly adapted to prevent condensation during compression at atmospheric pressure, even a'reduction of the quantity of-vapor condensed is of great advantage and I contemplate the use of the method of reducing condensation even if it is not eliminated.

My rocess is not to be limited by any theory o the mechanism of the process or by any example which may be given by way of explanation or illustration, but only by the following claims in which I wish to claim all novelty inherent in my invention.

I claim:

1. The method of compressing through a vacuum pump vapors which condense on adiabatic compression, which comprises actuating the pump abiabatically to draw the vapors from a body thereof in a confined stream under less than atmospheric pressure, heating the stream of vapors on the intake side of the pump to at least the temperature of their dew point at pressures greater than the pressure in the intake, and delivering the vapors from the pump under said increased pressures.

2'. The method of compressing through a vacuum pump vapors which condense on adiabatic compression, which comprises actuating the pump adiabatically to draw the vapors from a body-thereof in a confined stream under less than atmospheric pressure, heating the stream of vapors on the intake side of the pump to at least the temperature of their dew point at atmospheric pressure, and delivering the vapors from the'pump under at least atmospheric pressures.

3. The method of compressing through a 05 vacuum pump vapors which-condense on adiabatic compression, which comprises actuating the pump adiabatically to draw the vapors from a body thereof in a-conlined stream under less than atmospheric pressure, ,cooling the confined stream on the intake side of the pump below the temperature of the'dew point of the vapors at the pressure of the stream whereby condensate is produced, separating residual vapors from the condensate, heating the residual vapors on the intake side of the pump to approximately the temperature of their dew point at increased pressures, and delivering thevapors adiabatically. from the pump under the said increased pressures.

4. The method of increasing-the fiow"of vaporsfrom a well, which comprises mechanically drawing vapors from the well in a confined stream under less than atmospheric pressure by an adiabatically operated vacuum pump, heating the vapors flowing from the well on the intake side of the pump to at least the temperature of their dew point at atmospheric'pressure, and delivering the vapors from the pump under at least atmospheric pressure.

5.y The method of increasing the flow of vapors from a well, which comprises mechanically drawing vapors in a confined stream from the well under less than atmospheric pressure by an adiabatically operated vacuum pump, cooling the vapors flowing from'the well on the intake .side of the pump below the temperature of the dew point v of the vapors at the pressure of the stream 100 whereby condensate is produced, separating residual vapors from the condensate, heating the residual vapors on the intake sideof the pump to at least the temperature of their dew point at atmospheric pressure, and de- 105 livering the vapors from the pumpunder at least atmospheric pressure. l

WARREN K. LEWIS.

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